明るさの最大値 フィルターは活性レイヤーもしくはその選択範囲の明るい部分を拡げ、 強調します。

For every image pixel, it brings the pixel Value (luminosity) into line with the upper value (the brightest) of the 8 neighboring pixels (3×3 matrix). So, a bright pixel is added around bright areas. An isolated pixel on a brighter background will be deleted. A larger bright area will dilate by one pixel in all directions.

On complex images, bright areas are widened and enhanced the same, and somewhat pixelated.

背景が単色ならこのフィルターはノイズを取り除きます。

This filter is found in the main menu under Filters → Generic → Dilate.